In the past decade, the performance of portable computing devices rose dramatically. As a result, the computing capacity of smartphones has become considerable and portable technologies such as smartwatches and smart bracelets have started to conquer the markets.
Techniques of wireless transfer of information and energy have also been worked out, of which NFC and Bluetooth Lowe Energy (BLE) systems represent the most widely used ones.
These techniques have, however, a limitation, namely even if the two devices which communicate with each other using either one of this technique are positioned to the close vicinity of each other, the speed of transferring information and/or energy within a unity time is limited, and the transfer of higher amount of information and energy requires a longer period
US publication US2002/0167500 A1 describes a smart electronic label employing electronic ink, wherein the label is a self standing portable device that has an e-ink type display on which information received through a host device can be displayed. The portable device receives energy and data from a host device by one of the aforementioned wireless connections, and the two devices have to be placed close to each other so that the transfer of information and energy can be resolved.
The specialty of e-ink displays lies in that they require energy and input signals only as long as the data to be displayed are transported to the e-ink display, and the new picture replaces the old one, and the display retains the displayed picture as long as a different information is sent to the portable device for being displayed which is controlled to replace the previously displayed information. The storage and display of the previously fed information does not require any energy.
This publication describes several ways how the portable device can be realized which includes a use in the form of bracelet.
The publication describes in detail how a network of devices (people) can be built who have a right to use the system and how to gain access to stored information of a predetermined number of pictures and how a user can choose one or more out of them for downloading and display on the portable device.
The publication is silent about the time required for placing the host and the portable devices in the immediate vicinity of each other so that the information present in the host computer can be sent to the host computer to replace the previously displayed picture (refreshing) and to provide sufficient amount of energy for the portable device required for its operation.
A typical e-ink display is the product of EPSON Type S1D13541 and it has a publicly available Hardware Functional Specification that discloses the need of the display for different voltages when the displayed picture should be refreshed. The refreshment process uses a firmware running on the portable device that uploads the controlling program of the e-ink or electrophoretic display then follows the uploading process stored therein, which uses a timing profile that is included in the algorithm stored in the controlling program of the internal memory of the display device and the timing profile includes waveform files. The waveform file set that is made available by the manufacturer of the display contains refreshing timing and waveform information and conditions for the complete range of the whole range of operating temperature of the display. The associated large set of data has to be uploaded by the control unit of the display each time before a refreshment process takes place which is connected with consumption of energy and time required for carrying out the pre-programmed protocol.
The need of supplying the required energy to the refreshment of the portable device constitutes a further problem as the wireless transfer of the required energy is a slow process, therefore any decrease of the energy required for the refreshment of the displayed image spares the time during which the portable device should be hold closely to the host device. The required energy and time also depend on the amount of data that should be supplied from the host device to the portable device and from the amount of processing steps and data exchange that take place during a refreshment cycle.
From the point of view of energy storage, the limited space in the portable device does not always allow the use of conventional rechargeable batteries, and often the energy can be stored in capacitors. The need of the display for different voltages at refreshment requires the use of a power supply that is capable of providing these separate voltages.